1. Field of the Invention
The invention relates to wound capacitors, and in particular to capacitors having alternating conductive and separating layers wound around a central core device, such as a mandrel.
2. Description of the Prior Art
Wound capacitors exist in many forms including electrolytic, paper and thin film capacitors, In an effort to keep the Equivalent Series Resistance (ESR) and the Effective Series Inductance (ESL) at a minimum, it is known to wind the capacitor layers in an extended-foil configuration. For example, see FLAT-PACK ELECTROLYTIC CAPACITORS FOR SWITCHED-MODE POWER SUPPLIES by Warren J. Clement, IEEE, pages 105-110 (1983). In the extended-foil configuration disclosed in this article, where the anode and cathode electrode layers extend beyond the dielectric layers of the capacitor winding, adjacent windings of each of these extended portions of the layers are pressed together to form a continuous electrical connection to the respective electrode along its length. This continuous connection significantly reduces both the ESR and the ESL from values achieved by a typical prior art connection means employing a plurality of conductive tabs attached to the electrode at intervals along its length. Unfortunately, the article does not disclose any specific conductive structures for making low-resistance and low-inductance electrical connections to the extended electrode portions. Such conductive structures must not only be configured to maintain the low ESR and low ESL (hereinafter referred to as low impedance) achieved by the continuous extended foil connections, but also must be chemically compatible with the electrode material and any electrolyte which might be used in the capacitor.
Although many patents are known for wound capacitors having low ESR and low ESL values, the means for making electrical connections to the electrodes of these capacitors tend to be complicated (and thus expensive to manufacture) or rely on thin foil strips having a relatively large resistance per unit length for making the connections. See for example U.S. Pat. Nos. 3518500, 3611051, 3654524, 3822397, and 4385342.